Objective To investigate the effects of Lycopene ( LP) on immune function of ovarian cancer rats′and its mechanism .Metho ds Sixty ovarian cancer rat models made by injecting ovarian cancer cell line NUTU-19 were divided into five groups randomly:model group,Cisplatin group(2 mg/kg)and LP(40,20,10 mg/kg)group,n =12;the LP and Cisplatin were given by intraperitoneal injection ,once every two days for 5 times.The rats general states and tumor growth conditions were observed ,the tumor tissue morphological changes was observed by H&E staining;the tumor weight ,inhibition rate,spleen lymphocyte transformation rate were de -tected;and the content of IL -2 and TNF-αin serum were detected .The present of CD4 +,CD8 +in blood were detected and the ratio of CD 4 +/CD8 +was calculated .Results The food situation of the rats in LP groups was improved,tumor was reduced,activity and hardness were poorer ,necrosis presented ,tumor cell shrinkage and oth-er pathological morphological changes appeared ,especially the rats in LP 40 mg/kg group .Compared with model group,the tumor weight in LP(40,20 mg/kg)groups was decreased,the inhibition rate and the spleen lymphocyte transformation rate were increased;the contents of IL-2 and TNF-αwere decreased;the CD8+present was de-creased,while the CD4 +present in LP 40 mg/kg group was increased,the ratio of CD4 +/CD8 +was increased. All of the difference above were significant (P<0.05,P<0.01).Conclusion LP can effectively improve the immune function of ovarian cancer rat;which perhaps relates to its effects of reducing the inflammatory cytokines levels and increasing the ratio of CD 4 +/CD8 +.